Method of fixing turbine blades in place



April 28, 1936. w. e. NOACK METHOD OF FIXING TURBINE BLADES IN PLACE Filed Oct. 4, 1953 N M iv iewTaR Patented Apr. 28, 1936 UNITED STATES PATENT OFFICE ius'rnon or FIXING TURBINE BLADES IN PLACE Application October 4, 1933, Serial No. 692,176

In Germany October 12, 1932 3 Claims.

In machine construction the best-known and mostly employed manner of fixing two parts is .by means of the screw. It would seem obvious to use the screw for fixing the blades of gas and steam turbines as well, by providing the root of the blade with a thread and screwing it into a corresponding threaded bore in the wheel rim or the drum, or into segments thereof, forming removable sets of blades. This method of fixing cannot, however, be adopted without some further expedient, as the passage shape and the blade thickness necessary for ensuring a proper conversion of energy in the blade entail such small pitches that it becomes impossible to screw in the blades, since each blade would foul the adjacent blade which had been screwed into place before it. The blade must therefore consist, as has already been proposed, of at least two pieces, namely of the screw threaded blade 20 core, which takes up the peripheral and centrifugal forces, and of the blade edges which act as a guide for the jet of steam or gas. These are fixed either individually or as a complete unit 0 to the blade core, after the blade core has been screwed in.

The present invention relates to a method of fixing blades of a tried shape and pitch, which 'consist of a single piece only, but which can nevertheless be fixed by screwing in. It consists O in bending over, after the blade has been made, one or both blade edges, thereupon screwing the blades into the wheel or drum and finally bending the edges back again. By bending over the 35 edges the overall size of the blade is 'reduced to such an extent that the blade can be turned for screwing it in.

Fig. 1 shows a few blades according to the invention in section and elevation and Fig. 2 is a plan of the same portion of the rimwhen developed, the blades in this example being such as have only one edge turned over. The blades are assembled one after the other from right to left, and in Figure 2 the blade 2, which has had its inlet edge turned over after manufacture, is 5 in a position for screwing in. After the blade has been screwed into place, theedge is bent into normal position, as shown in dotted lines for the blade 3. For unbending a press is used, which effects the bending, back and smoothing out of the blade in several operations. In order to be able to screw in the thread tightly and yet to get the blade into the correct position, packing discs of diiferent thickness are provided, the selection of which is determined by experimental screwing in. 4 is a packing disc of this kind. In order to prevent the blade from turning the base of the screw is secured for instance by electric spot welding at 5. This method of fixing blades can be employed with advantage for cooled blades as well.

What I claim is:

1. In the fixing of a screw-in turbine blade next to a blade already in place, the steps which I" consist of reducing by deformation the dimensions of the blade referred to the axis of screwing, screwing the blade in, and restoring the blade to its former shape.

2. In the fixing of a screw-in turbine blade "I next to a blade already in place, the steps which consist of bending over one edge of the blade, screwing the blade in. and bending the edge back. 7

3. In the fixing of a screw-in turbine blade next to a blade already in place, the steps which consist of bending over both edges of the blade, screwing the blade in, and bending the edges back.

WALTER GUSTAV NOACK. 

